The Internet is based on a client server model and comprises a plurality of web servers which are accessible by a plurality of clients over a communication network.
The notion of access to web services via the Internet is becoming popular and a number of standards are developing.
FIG. 1 shows a computer network 5 comprising a host computer system, web server 50, connected to client 10 over communication network (e.g. the Internet) 60. The web server 50 hosts access to a web service 30 which provides a collection of functions packaged as a single entity and published to the network for use by other programs, thus supporting interoperable machine-to-machine interaction over the network. The web service has an interface 40 that is described in a machine processable format, such as the Web Services Definition Language (WSDL). Other systems interact with the web service in a manner prescribed by its interface using messages. These messages are typically conveyed using HTTP and normally comprise extensible Markup Language (XML) in conjunction with other web-related standards.
The WS-Addressing specification is the result of a collaborative effort driven by the W3C (World Wide Web Consortium). WS-Addressing is concerned with the targeting of web service messages appropriately.
WS-Addressing introduces the notion of EndpointReferences (EPRs) which convey the information required to address a web service endpoint (a web service port with some possible application data associated) in a standard XML format.
There are a number of properties in an EPR such as its address (which is the URI of the endpoint that the EPR represents), and metadata about the endpoint (such as the capabilities of the endpoint). Some of these properties (such as the address URI) may be generated based on the endpoint's deployment information or they may be known to the application generating the EPR. EPRs are propagated in a SOAP Envelope as part of Web service interactions. The recipient of an EPR in a Web service interaction might use that EPR in order to target the Web service.